It is a structure under which ants of the genus Allomerus decemarticulatus hide and wait for their prey to walk over the entrances.
Its made of fibers of their host plant Hirtella physophora, fixed with a symbiotic ascomycete fungus.

I know I know, it’s part of the carton that Allomerus construct in some myrmecophyte. The one I know is Allomerus demerarae and Cordia nodosa. It’s their special carton construction over the branches and domacia to sit and wait and ambush their prey!

Well, I met them as Allomerus demerarae in southeast Peru. According to the antweb, it’s a senior synonym for A ortoartuculatus, that apparently is a subspecies of A decermaticulatus. This particular mutualism in southeast Peru was with Cordia nodosa, but this genus can built the same cartons in other myrmecophytes different from C. nodosa in different regions. If I could see in the pic some feature of the plant, maybe I could tell